Heat exchangers of this type are often manufactured in large series e.g. for use in dwelling houses to provide hot water for household use and/or for heating purposes. Other applications include use in heat pumps and air conditioners.
In known heat exchangers of this type the brazing of pairs of plates around port holes is performed in a ring shaped area located in a single plan—the plan of the edge of the sort holes. The port holes are located at least at such a distance from the outer periphery of the exchanger as to allow a reliable sealing around the port holes.
Heat exchangers of this type have been described e.g. in EP 1 +94 291 A, U.S. Pat. No. 4,987,955 A and in U.S. Pat. No. 5,988,296 A. In all these known heat exchangers it is necessary to flush and shake to obtain an effective cleaning. Also a part of the heat exchanger does not offer the best possible capacity of exchanging heat.